Two questions here - I am still cycling my new 75g, doing it the slow way with mostly dry rock and a little live rock. I have noticed the last few days some growth on the live rock, which I assumed was algae, and it has started spreading quickly. Being new to this, though, I started wondering today if it could be cyanobacteria rather than the algae I know I should expect during the cycle. I have never seen cyanobacteria in person so I don't have a reference point.
I'll try to attach pictures.

My second question - in regards to CUC, do I add an entire crew at once, or small numbers at a time? And do I wait until ammonia is all the way down to 0?
Thanks!

I recommend shutting the lights off while cycling. The nutrient levels are high at this point and that plus light is a perfect situation for all sorts of nuisance algae.
You really don't need a clean up crew at all, and chances are in a brand new tank you'll be starving most of them to death.